PHYS 1600 : Chapter 17

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silvergoat980

13 Dec 2011

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Powerhouse"-that blazes with the luminosity of 100 galaxies. Other active galaxies: powerful energy sources in space other than quasars include seyfert galaxies, radio galaxies, double-radio sources, and bl lacertae objects. Although their energy source is very small, like that of a. Have unusually bright, starlike (that is, a pinpoint as seen form earth) nuclei. Their spectra do not look anything like a star"s blackbody spectrum they have strong emission lines. Many are highly variable, meaning that their brightness levels change in different parts of the electromagnetic spectrum. They have jets of electrons and protons and beams of radiation emanating from their cores like the emissions observed for 3c 273. Such galaxies are called peculiar galaxies: galaxies with two radio lobes are called double-radio sources. These are the bl lacertae objects: a bl lac"s most intriguing characteristic is an unusually weak set of spectral lines.

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Introduction. Telescope time is a valuablecommodity in astronomy, so astronomers plan their observationscarefully. One of the first steps is to choose what type ofobservation to make. Recall that three basic types of astronomicalobservation are imaging (taking a photograph of anobject), spectroscopy (spreading an object's light into aspectrum), and timing (measuring how an object's lightvaries with time).

Part A: Sort each of the astronomical questionsbelow into the appropriate bin based on the type of observation youwould need to perform to answer it.

Three Categories: Imagine, Spectroscopy andTiming

The Questions:

1. "What are the major surface features of Mars?"

2. "What is the temperature of Jupiter's atmosphere?"

3. "Does the star Mira vary in brightness?"

4. "How large is the Andromeda Galaxy?"

5. "What is the chemical composition of the Crab Nebula?"

6. "Is the X-ray emission fro the galactic center steady orchanging?"

7. "Is the star Vega moving toward us or away from us?"

8. "Are stars in the Orion Nebula surrounded by dusty disks ofgas?"

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Introduction: Different telescopes areoptimized for observing different wavelengths of light, so anotherconsideration in planning an observation is deciding what type oftelescope to use.

Part B: Each of the following statementsdescribes an astronomical measurement. Place each measurement intothe appropriate bin based on the type of telescope you would use tomake it.

Three Categories: Infrared Telescope, VisibleLight Telescope and X-Ray Telescope

The Statements:

1. Study a dense cloud of cold gas in space.

2. Measure the brightness of a star that is similar to ourSun.

3. Observe the hot (1-million K) gas in the Sun's corona.

4. Obtain a spectrum of sunlight reflected by Mars.

5. Determine the surface temperature of Venus.

6. Look for high-energy radiation from a supernova.

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PHYS 1600 : Chapter 17

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